This invention relates to apparatus for use in handling a load which is capable of raising and lowering, or of towing, a load and also handling service cables and/or hoses connected to the load. The invention is particularly, but not exclusively, applicable to the handling of subsea equipment such as grabs.
Hitherto, providing services to underwater equipment has required the provision of a specific bundle of cable(s) and/or hose(s) dedicated to each application. For some applications, it is known to incorporate the service bundle within an armored hoist rope. This approach has a number of deficiencies. The resulting rope is costly, gives inferior hoisting properties, and by virtue of limitations on the diameter of rope which can be handled the services which can be incorporated are limited. Further, in practice it is impossible with this arrangement to add to the length of the rope or to join different types of materials, for example wire ropes with fiber ropes.
It is also known from our previous application PCT/GB96/00158 to wrap service cable around a rope being paid out, and to unwrap the service cable from the rope as the rope is recovered.
According to the present invention there is provided apparatus for use in handling a load comprising a load-bearing rope, a mechanism for paying out and recovering the rope, a first service cable holder for holding a first service cable with a length of the first service cable extending therefrom, a second service cable holder for holding a second service cable with a length of the second service cable extending therefrom, and a wrapping device for rotating said lengths of service cable around the rope as the rope is payed out to wrap the service cables around the rope, wherein one of the first and second service cables is wrapped over the other.
The service cable holders can be drums.
Typically the wrapping device can recover the service cables to their respective drums during recovery of the rope and cables.
The term xe2x80x9cservice cablexe2x80x9d is used herein to denote a flexible elongate member used for conveying power or data, such as an electrical cable, a fiber optic cable, or a pneumatic or hydraulic hose.
Preferably, the service cables are wrapped helically around the rope.
Typically, the load-bearing rope will be a hoist rope used for raising and lowering a load. Alternatively, the load-bearing rope may be a towing rope used for paying out, towing and recovering a load such as a marine sensor array.
Preferably, the mechanism for paying out and recovering the rope comprises a rope winch, from which the rope passes over a rope sheave and thereafter extends to the load along a substantially straight axis.
The wrapping device may comprise the or each service cable drum being arranged for rotation about a drum axis which coincides with said axis, the drum typically having a central aperture through which the load-bearing rope passes, said length of service cable preferably passing over a service cable sheave which is mounted for movement in a circular path around said axis.
Alternatively, the or each service cable drum may be rotatable on a structural member which is arranged for movement in a circular path about said axis.
The hoist rope winch, the or each service cable drum, and the wrapping device may conveniently each have a respective driving motor; they could however be driven by a single source through appropriate mechanical linkages.
The first and second cables are typically wrapped around the rope in different directions; for example, the first cable can be wrapped onto the rope in an anticlockwise direction and the second cable can be wrapped around the rope in a clockwise direction so that one cable overlays the other. This option is to be preferred but the invention can also work well with the service cables being wrapped in the same direction but at different pitches of helix, so that one overwraps the other.
The invention also provides apparatus for use in handling a load comprises a load-bearing rope, a mechanism for paying out and recovering the rope, a mechanism for holding and paying out a service cable and a wrapping device for rotating one of the service cable and the rope around the other as they are payed out to wrap the said one of the service cable and the rope around the other, and to unwrap one of the service cable and the rope from the other as it is recovered, wherein at least part of the wrapping device can be moved to accommodate large objects.
In a preferred embodiment the service cable is provided on drum which is mounted on an arm which rotates around the axis of the rope. The drum can be arranged to rotate about a horizontal or a vertical axis.
The service cable holder is preferably mounted on an arm that is preferably hinged to a frame and can be provided with a lifting mechanism such as a hydraulic ram to lift the arm with respect to the frame. Instead of a hydraulic ram the lifting mechanism may be a screw-driven mechanism which can be electrically or hydraulically powered.
The invention also provides apparatus for use in handling a load comprising a load-bearing rope, a mechanism for paying out and recovering the rope, a drum for holding a service cable with a length of the service cable extending therefrom, and a wrapping device for rotating said length of service cable around the rope as the rope is payed out to wrap the service cable around the rope, and to unwrap the service cable from the rope as the rope is recovered, wherein the wrapping device rotates around the axis of the rope, but does not rotate about its own axis.
The invention also provides apparatus for use in handling a load comprising a load-bearing rope, a mechanism for paying out and recovering the rope, a cable holder for holding a service cable with a length of the service cable extending therefrom, and a wrapping device for rotating said length of service cable around the rope as the rope is payed out to wrap the service cable around the rope, and having at least one slot to facilitate attachment of the apparatus to the load-bearing rope.
The invention also provides a method for use in handling a load, the method, comprising paying out a load-bearing rope and wrapping first and second service cables around the rope as it is payed out, and subsequently unwrapping the service cable from the rope as the rope is recovered, wherein one of the service cables is wrapped over the other.